Knives are, of course, one of the oldest and well known tools. Knives of the folding type typically include a blade pivoted directly to the handle. Springs, locks and mechanisms of all kinds have been attached to such basic structure. The problems, in general, with such mechanisms has been that such mechanisms tend to fail eventually, they are complicated to produce, the knives so produced are not strong or secure and thereby are prone to breakage and they are expensive to manufacture.
A traditional lock back knife uses an elongated leaf spring to hold the blade in a locked position. Pushing on one end of the leaf spring releases the blade to allow it to pivot. Wear between the leaf spring and the blade will eventually cause the blade to be loose in the locked position thereof.
Consequently, there is a need for a folding knife which is economical to mass produce, dependable to use and one which is not susceptible to looseness despite wear on the locked parts.